ASEXUAL REPRODUCTION IN SAGARTIA 167 



FISSION AND REGENERATION 



The frequent occurrence of fission in this species has been 

 noted by Davenport ('03) and the process has been well de- 

 scribed by Hargitt (14). A very similar process has been de- 

 scribed for a closely related form by Torrey and Mery ('04). 

 The process apparently consists simply in the tearing of an 

 individual into two parts by the migration of two portions of 

 the basal disc in opposite directions. The first suggestion of an 

 approaching division is seen in the elongation of the base from 

 its usual nearly circular outline to an oval form. In the course 

 of a few hours or days this elongation becomes more extreme. 

 The whole body becomes flattened closely against the sub- 

 stratum, evidencing a state of extreme tension. Eventually a 

 rent occurs in the base. This rent widens, gradually extends 

 up the column and finally involves the oral disc and the esopha- 

 gus. Division may result in the production of more than two 

 pieces almost simultaneously; although, as I shall show (p. 173), 

 this occurs really by successive fissions rather than by simul- 

 taneous division into three or more parts. I believe that the 

 mouth and esophagus are invariably cut by the plane of fission. 

 There is no suggestion of a division resembUng that known as 

 basal fragmentation. Any other method of asexual repro- 

 duction than that described above must be very rare in the 

 adult form of this species. 



Certain external features of the process of reconstruction 

 following division in S. luciae have been described by Davenport 

 ('03), and in S. davisi by Torrey and Mery ('04). 



After fission is accomplished, the two resulting individuals re- 

 main in a limp state closely pressed to the substratum, and the 

 torn edges of each slowly roll inward and fuse. Within a day 

 or two the separate pieces, their wounds having closed, acquire 

 the normal upright position and typical cylindrical form, and 

 the tentacles become expanded. For some days after this the 

 region of fusion of the edges shows as a narrow vertical streak 

 of much hghter color than the adjacent old parts of the column. 

 At this stage in less briUiantly colored specimens the new tissue 



